[fix/docs]: Memory leakage caused by using new operator & refactoring/documentation (#1428)

* fix: Fixed memory leak bug by using 'std::vector' instead of 'new'

* Small refactoring

* Small refactoring

* Fix Code Formatter test failed

* Code refactored based on PR review

* Added return 0 based on PR review

* docs: Added documentation for linear queue using array implementation

* docs: Updated based on PR review

* docs: Second update based on PR review

* docs: Updated based on PR review

* Change max_size data type

* Use std::array instead of std::vector

data_structures/queue_using_array.cpp

@@ -1,77 +1,120 @@
-/*
-    Write a program to implement Linear Queue using array.
+/**
+ * @file
+ * @brief Implementation of Linear [Queue using array]
+ * (https://www.geeksforgeeks.org/array-implementation-of-queue-simple/).
+ * @details
+ * The Linear Queue is a data structure used for holding a sequence of
+ * values, which can be added to the end line (enqueue), removed from
+ * head of line (dequeue) and displayed.
+ * ### Algorithm
+ * Values can be added by increasing the `rear` variable by 1 (which points to 
+ * the end of the array), then assigning new value to `rear`'s element of the array.
+ * 
+ * Values can be removed by increasing the `front` variable by 1 (which points to 
+ * the first of the array), so it cannot reached any more.
+ * 
+ * @author [Pooja](https://github.com/pooja-git11)
+ * @author [Farbod Ahmadian](https://github.com/farbodahm)
+ */
+#include <iostream> /// for io operations
+#include <array>   /// for std::array
 
-    Functions to implement
-        Enqueue (Insertion)
-        Dequeue (Deletion)
+constexpr uint16_t max_size{10}; ///< Maximum size of the queue
 
-*/
-#include <iostream>
+/**
+ * @namespace data_structures
+ * @brief Algorithms with data structures
+ */
+namespace data_structures {
 
-#define MAXSIZE 10
+/**
+ * @namespace queue_using_array
+ * @brief Functions for [Queue using Array]
+ * (https://www.geeksforgeeks.org/array-implementation-of-queue-simple/) implementation.
+ */
+namespace queue_using_array {
 
+/**
+ * @brief Queue_Array class containing the main data and also index of head and tail of the array.
+ */
 class Queue_Array {
-    int front;
-    int rear;
-    int size;
-
- public:
-    Queue_Array() {
-        front = -1;
-        rear = -1;
-        size = MAXSIZE;
-    }
-    int *arr = new int[size];
-    void enqueue(int);
-    int dequeue();
-    void display();
+public:
+    void enqueue(const int16_t&);  ///< Add element to the first of the queue
+    int dequeue();                ///< Delete element from back of the queue
+    void display() const;         ///< Show all saved data
+private:
+    int8_t front{-1};             ///< Index of head of the array
+    int8_t rear{-1};              ///< Index of tail of the array
+    std::array<int16_t, max_size> arr;    ///< All stored data
 };
 
-void Queue_Array::enqueue(int ele) {
-    if (rear == size - 1) {
+/**
+ * @brief Adds new element to the end of the queue
+ * @param ele to be added to the end of the queue
+ */
+void Queue_Array::enqueue(const int16_t& ele ) {
+    if (rear == arr.size() - 1) {
         std::cout << "\nStack is full";
     } else if (front == -1 && rear == -1) {
-        front = rear = 0;
+        front = 0;
+        rear = 0;
         arr[rear] = ele;
-    } else if (rear < size) {
-        rear++;
+    } else if (rear < arr.size()) {
+        ++rear;
         arr[rear] = ele;
     }
 }
 
+/**
+ * @brief Remove element that is located at the first of the queue
+ * @returns data that is deleted if queue is not empty
+ */
 int Queue_Array::dequeue() {
-    int d;
+    int8_t d{0};
     if (front == -1) {
         std::cout << "\nstack is empty ";
         return 0;
     } else if (front == rear) {
-        d = arr[front];
+        d = arr.at(front);
         front = rear = -1;
     } else {
-        d = arr[front++];
+        d = arr.at(front++);
     }
 
     return d;
 }
 
-void Queue_Array::display() {
+/**
+ * @brief Utility function to show all elements in the queue
+ */
+void Queue_Array::display() const {
     if (front == -1) {
         std::cout << "\nStack is empty";
     } else {
-        for (int i = front; i <= rear; i++) std::cout << arr[i] << " ";
+        for (int16_t i{front}; i <= rear; ++i) std::cout << arr.at(i) << " ";
     }
 }
 
-int main() {
-    int op, data;
+}  // namespace queue_using_array
+}  // namespace data_structures
 
-    Queue_Array ob;
+
+/**
+ * @brief Main function
+ * @details
+ * Allows the user to add and delete values from the queue.
+ * Also allows user to display values in the queue.
+ * @returns 0 on exit
+ */
+int main() {
+    int op{0}, data{0};
+    data_structures::queue_using_array::Queue_Array ob;
 
     std::cout << "\n1. enqueue(Insertion) ";
     std::cout << "\n2. dequeue(Deletion)";
     std::cout << "\n3. Display";
     std::cout << "\n4. Exit";
-    while (1) {
+    while (true) {
         std::cout << "\nEnter your choice ";
         std::cin >> op;
         if (op == 1) {
@@ -89,4 +132,6 @@ int main() {
             std::cout << "\nWrong choice ";
         }
     }
+
+    return 0;
 }